The 34-year-old scored in his homeland with an acrobatic overhead but Gala bossed the remainder of the half and led at the interval through Sinus Gumus and Bruma.
Wayne Rooney turned the game on its head for a much-changed Reds side with a quickfire brace after the break and further goals from Marouane Fellaini and Juan Mata added gloss to the scoreline.
The result was largely a footnote, but the presence of Ibrahimovic in the United line-up ensured that this was far from a routine friendly and he justified the attention with an impressive impact.
Zlatan met Antonio Valencia's run and cross with a typically athletic bicycle kick that bounced into the turf and beyond the sprawling Fernando Muslera inside five minutes.
Ander Herrera went close but despite rarely threatening up until then, the Turkish side were level on 22 minutes.
Having put the Reds ahead, Ibrahimovic conceded the set piece from which one-time United target Wesley Sneijder picked out Gumus to head home beyond David De Gea.
Suddenly, Galatasaray assumed control as the Spaniard saved twice in quick succession- first from Sneijder and then Yason Oztekin.
He was powerless to prevent the Turks taking the lead, however, when Bruma played a one-two with Gumus and curled in a beauty from 20 yards with five first half minutes to play.
Jose Mourinho made five changes at the break and it did not take long for his new look- literally- (United were playing in the new white away kit)- to equalise upon the resumption.
Marcus Rashford fed Valencia whom in turn burst free down the right and crossed for Rooney to slam in a finish from close range on 55 minutes.
Shortly afterwards, United found themselves ahead thanks to a sensational piece of skill and pace from Rashford.
The young striker raced on to Rooney's excellent through ball to skip past Serdar Aziz, burst into the box and looked poised to shoot until he went down under a challenge from the onrushing Muslera.
Rooney stepped up to fire in the resultant spot-kick and, from then on, the rampant Reds never looked back.
Marouane Fellaini looped home an excellent header from Valencia's cross at the culmination of a neat move, De Gea saved well from Oztekin at the other end before a further six substitutions from Mourinho.
Carrick and Mata linked up for the latter to sweep in the fifth to complete what was now a rout as United warmed up for next week's Community Shield match in style in Gothenburg.
United: De Gea (Romero 67); Valencia (Memphis 67), Bailly (Rojo 67), Blind (Jones 67), Shaw (Darmian 67); Schneiderlin (Carrick 46), Herrera (Fellaini 46); Mkhitaryan (Lingard 46), Rooney (Mata 67), Martial (Young 46); Ibrahimovic (Rashford 46).
Man of the Match: Antonio Valencia.